The CNS is a site of persistent HIV replication and progressive neuropathological damage even in individuals receiving highly active antiretroviral therapy (HAART). CNS HIV reservoirs include both microglia and astrocytes; however, factors controlling HIV replication in these cell types, and the role of microglia and astrocytes in promoting the neurodegeneration characteristic of HIV-associated dementia (HAD) are not fully understood. This represents a large obstacle to the development neuroprotection against HAD. For the next cycle of this program project we propose to further our studies of HAD neuropathogenesis with 4 interactive projects. Dr. F. Gonzalez-Scarano will continue his studies of HIV infection of microglia, with a focus on the role of the association of HIV gag protein with specific exosomal proteins in promoting virus assembly and production in activated macrophages and microglia. Dr. D. Kolson will focus on the mechanisms of astrocyte injury and dysfunction that contribute to neuronal damage, utilizing an in vitro model he recently developed and the technology of in vivo single-cell RNA profiling. Dr. R. Pomerantz, will determine the mechanisms of restriction of HIV replication in astrocytes, based on interactions his group has identified between an astrocytic cellular helicase and the viral regulatory protein Rev. Dr. R. Collman will study the molecular pathways by which HIV triggers macrophage activation through Env/CD4/chemokine receptor interactions, to initiate cascades of cellular activation and mediator secretion that ultimately result in neuronal and glial cell damage. The coordinated studies in this program project will increase our understanding of critical mechanisms of virus persistence and of the pathophysiology of neurodegeneration and provide novel targets for prevention or intervention in HAD.